This invention relates to insulated duct systems.
Insulated duct is widely employed in buildings for conveying heated air or cooled air for temperature control of interior environment. Typically such systems are fabricated and installed on the job, in piecemeal fashion, with tremendous waste of material being common. Skilled craftsmen are necessary for interfitting sheet metal sections and flexible duct sections to form the duct network, but little effort is applied toward optimum use of materials, such that a completed system typically is accompanied by piles of wasted scrap sheet metal components, insulation, insulated flexible duct, and related materials. It is considered more economical to allow the highly paid craftsmen to waste material than to spend the time for determining optimum usage thereof. Moreover, it is difficult to try to optimize air flow through the various branches of the duct system. Thus, a small room supplied by the system might receive tremendous air flow while a much larger room might only receive minimal air flow. Flow restricting baffles are then inserted in register faces in an effort to alter such conditions, resulting in substantial air flow inefficiencies, audible whistling effects, and distracting "howling" sounds when air flow through large ducts is started and stopped.
Even with skilled craftsmen, the assembly techniques commonly used usually result in leakage of the conveyed air. To overcome such leakage, which results in inefficiency, poor air flow, noise and condensation, ducting tape is liberally applied around all of the joints, somewhat comparable to covering wounds with a generous supply of bandages. Ducting tape notoriously breaks loose in time, resulting in lost efficiency and higher energy usage.
In the particular problem area of the connection of an insulated duct to a duct board opening, one known technique is to place a clamp around the joint and then wrap the entire area in ducting tape. But, as noted above, taping is a poor temporary solution. Another technique is to place a plastic or duct board ring around the end portion of the duct, inside of the exterior jacket of the insulated duct, and then insert the duct with its insulating jacket into the opening until the ring abuts the duct board. But, air still leaks out between the duct board and the jacket to create problems.
In an attempt to overcome some of the above-noted prior art problems, the assignee of the present invention manufactured and sold a duct system including a plurality of duct assemblies interconnected using transition components. Each duct assembly included a flexible insulated duct having rigid sleeves inserted at either end thereof. The duct was taped to the sleeve using duct tape, which as noted above is an inefficient manner of interconnecting such components. The transition components each included a plurality of duct board panels taped together to form an enclosed polyhedron. These transition components proved to be of insufficient strength in installation and actual use. The taped duct board panels also suffered the disadvantages noted above in conjunction with taping. To interconnect these elements, the duct sleeves were inserted through openings cut in the duct board transition components; and bendable sleeve tabs were bent to retain the sleeves within the transition components.